I guess it's also part of not wanting to admit that our bosses screwed up royally when they interviewed her and missed all clues that she wouldn't be able to cut it. It's reflecting bad on them if they had to admit to our department boss that she's not up to it because they may be asked why the interview didn't show any flaw and why she was kept after her 6 month probationary time so that's why she was kept and supported so much (also we have a huge workload sometimes and every person missing makes it ten times worse for others who have to pick up the work).
I shudder to think who else must have applied that she was the best choice, anyway.. i basically only have to tolerate her for 2 weeks now but i get uncharacteristically aggressive whenever she opens her mouth.. she think's she's funny but she's not, she tells all this personal stuff that nobody asked for and nobody cares about and she's just grating.
Her replacement has already started to work her but after a week you can't tell anything (also he was gone most of the week on our customary company tour through various departments so he gets to know the whole company). Fingers crossed he'll turn out better than her.